Intro to Ecology Flashcards
Ecology
scientific study of interactions of organisms with their physical environment and with each other
major goal of ecology
to explain the abundance and distribution of organisms
historically, ecology was a what kind of science?
observational and often descriptive
modern ecology includes:
observation and experimentation
experimental ecology
manipulation of organisms or their environments to determine mechanisms governing abundance and distribution
the current abundance and distribution of kelp is a result of ________.
predation
true or false:
ecology and evolutionary biology are closely related disciplines
true
-events occurring in ecological time (minutes, days, years) translate into effects over evolutionary time (decades, millennia)
evolutionary ecology
examines how interactions between and within species evolve
-ex. hawks feeding on mice impact traits of a mouse population
ecologists work at levels ranging from individual organisms to the biosphere
-hierarchy of life
levels of organization
- population ecology
- community ecology
- ecosystem ecology
population ecology
-focuses on interactions of individuals within a population
community ecology
- focuses on groups of interacting populations of different species that live in the same place at the same time
- community refers to a group of humans who live and interact in the same small geographic location
- gold community
- ecological community includes all organisms s that live/ interact with us in space and time
ecosystem ecology
- the integrated study of living (biotic) and nonliving (abiotic) components of an environment
- major focus on energy flow across the hierarchy of life
- food chains/ webs, trophic levels
abiotic factors
nonliving part of the environment such as temperature, light, moisture, nutrients, pH, salinity, pressure
biotic factors
the living organisms
-ex. plants, animals, fungi, protists, bacteria
what does biosphere include
it includes the earth’s surface, atmosphere and hydrosphere that are occupied by living organisms
-all ecosystems of aquatic and terrestrial realms
populations change through time and vary from place to place
-predicting this change requires understanding of:
- population characteristics
- life history strategies
- population dynamics
- population growth
populations are characterized by
- geographic range
- spatial distribution
- size
- density
- demography
geographic range
- overall spatial boundaries within which it is found
- within that range, each population occupies a habitat
- example: penguins!
- southern hemisphere
- each species of penguin has a smaller range
- and each population of penguins inhabits only a part of that smaller geographic range
habitat
a specific environment in which an organism lives
spatial distribution
populations vary in dispersion, how individuals are distributed within the geographical range and why
random dispersion
individuals are distributed unpredictably within a uniform habitat
clumped dispersion
individuals group together due to patchy habitats, social groups, or reproductive patterns
uniform dispersion
individuals repel each other and are evenly spaced because resources are in short supply
-intraspecific competition
population size
number of individuals in a population at a given time
population density
number of individuals per unit of habitat
-individuals/km
estimating population size and density
- for large bodied species, a simple head count provides accurate information
- for tiny organisms at high densities (phytoplankton), population size extrapolated from counts of samples
- for mobile animals within a restricted geographic range, mark-release-recapture sampling
demography
the statistical study of precesses that change a population’s size and density through time
-population structure
which demographic processes affect size and composition of a population
births, deaths, immigration, and emigration
life tables summarize population structure
data on births, survival and mortality of individuals within a population
cohort life tables monitor what?
a cohort (individuals of same age) from birth to death
data can be compared from one cohort to another to:
analyze variation in survival, mortality over time
life tables can also summarize fecundity of a population
to determine mean reproductive rate at each age
-ex. proportion of female squirrels weaning a litter, or mean size of litters, or the age when females are most fecund
timing of demographic processes is important
population with high juvenile mortality will have different structure than one with high mortality in post- reproductive years
survivorship curves
show rate of survival for individuals over the average life span of the species
three types of survivorship curves
type 1
type 2
type 3
type 1 curves
- reflect high survivorship until late in life
- typical of large animals that produce few young and provide lots of parental care
- humans, large mammals
type 2 curves
(negative slope)
- show a constant probability of dying at any age
- some lizards, rodents, perching birds
type 3 curves
(opposite of log graph)
- reflect high juvenile mortality, followed by a period of low mortality once offspring reach a critical size
- oak trees, shrubs, free spawning marine invertebrates
life history theory
states that lifetime strategies of growth and reproduction are shaped by natural selection to produce the largest possible number of viable offspring
life history strategies include
- # of lifetime reproductive episodes
- semelparity-iteroparity
- number, size and care of offspring
- r/K selection
semelparous
- single reproductive episode before death
- devote all stored energy to a single reproductive event
- ex.
- coho salmon
- larval salmon feed and grow for about 1 year before swimming to the ocean
- coho salmon
- 1 to 2 years later return to natal rivers to spawn… and die
another examples for semelparity
- annual plants, bacteria, many invertebrates
- agave (vegetative growth can last up to 25 years, but also produces asexual clones)
- giant pacific octopus
- females produce a single touch clutch of offspring brooding them for about 6 months in a “den”. females die shortly after young hatch
iteroparous
- multiple reproductive events over a lifetime
- part of energy budget is reserved for growth and maintenance
- example
- sea turtles
- females come ashore and lay eggs in a hole and head back to sea
- provide no protection to offspring, many will not survive
- females will reproduce again the next year
- sea turtles
other examples of iteroparous
- pine and oak trees
- most mammals (including us)
- all birds
r/K selection
refers to selection of traits that trade off between quantity and quality of offspring
r-selected species
- generally small, with short generations times
- produce numerous offspring sometimes in a single reproductive event
- semelparous
- little to no parental care to offspring
k-selected species
- generally large, with long generation times
- multiple reproductive episodes over lifespan
- iteroparous
- produce very few, high quality offspring
- offspring receive substantial parental care
- type 1 or type 2 survivorship
- thrive in stable environments: may use behaviors and physiology to buffer against environmental change
trade-offs in number, size and care of offspring
- the larger an organisms’s investment in each individual offspring, the fewer offspring it can produce
- investment includes energy, resources, and time traded for alternative activities such as foraging
- example: broadcast spawners release thousands of eggs per spawning versus caring for a mere hundred offspring
trade offs in these different life history strategies
- organisms allocate limited energy or resources to one strategy at the expense of another
- reproduce oce or many times; produce few, well- provisioned offspring or thousands left to fend for themselves
strategies evolve to optimize:
traits that maximize fitness
